Production of Epoxy Resin from Local Cashew Nut Shell Liquid in Edo State

Cashew nut shell liquid, a by-product of cashew processing, is available in substantial quantities in Edo State, South South Nigeria, yet remains largely unutilised by local industries. This study investigates the synthesis of epoxy resin from cardanol, the main phenolic constituent of cashew nut shell liquid extracted from processors in Auchi, Edo State. The liquid was extracted from cashew shells by solvent extraction using acetone, and cardanol was isolated by vacuum distillation. Epoxidation of cardanol was carried out using epichlorohydrin in the presence of sodium hydroxide catalyst at 80 degrees Celsius for 4 hours. The produced epoxy resin was characterised for epoxide equivalent weight, viscosity, gel time, flexural strength, tensile strength, impact resistance, and thermal stability by thermogravimetric analysis. The effect of different curing agents, specifically triethylenetetramine and dicyandiamide, on mechanical properties was also evaluated. Results showed that cardanol-based epoxy cured with triethylenetetramine exhibited tensile strength of 38.4 MPa and flexural strength of 52.1 MPa, meeting performance thresholds for general-purpose coating and adhesive applications. Gel time of 18 minutes at 25 degrees Celsius provides adequate working time for practical application. The thermal decomposition onset temperature of 280 degrees Celsius confirmed suitability for elevated-temperature environments. The study establishes cashew nut shell liquid from Edo State as a viable bio-based raw material for local epoxy resin production. Keywords: cashew nut shell liquid, cardanol, epoxy resin, bio-based polymer, Edo State